Gravel packing of a well is a recognized technique for preparing a formation for production and for improving a well's production characteristics. Gravel packing is generally carried out by pumping gravel-containing fluid down into the zone of the formation to be treated and filtering the returning fluid to insure that the gravel is deposited in the desired zone. The goal of gravel packing is to force gravel out of the well casing and into the producing formation. However, the gravel-containing fluid must be pumped through the interior of the down hole equipment string to prevent losses and contamination between the surface and the desired zone. At some point, it is necessary to use a bypass tool to switch the flow of gravel-containing fluid from the interior of the equipment string to the exterior of the string so that the fluid may be used to gravel pack the formation. The bypass tool must direct the downward-traveling fluid outward, and simultaneously direct the upward-traveling return fluid from the interior of the equipment string to the exterior for the return trip to the surface.
Current bypass tools restrict the maximum rate of flow to about fifteen barrels per minute. This restriction is caused by the fluid pathway used to exchange the positions of the fluid streams. The downward-flowing path requires a series of sharp tums which causes flow rate losses and subjects the tool to relatively high rates of erosion. This series of tums usually entails at least four right-angle tums to redirect the gravel bearing fluid from the tool's interior to its exterior. Because of this flow rate restriction, the pressure that can be used to gravel pack a formation is restricted. However, it is desirable in some cases to provide a gravel packing flow rate in excess of twenty barrels per minute or more to maintain higher gravel packing pressures. These higher pressures would allow gravel to be forced further into formation fractures, improving well production rates.
It is therefore desirable to have a bypass tool that allows higher flow rates, and accordingly higher treatment pressures, than present tools. This goal is accomplished by providing a tool which utilizes enlarged flow areas and direct exit ports to direct the flow of downward-traveling fluid from the interior to the exterior of the tool. In this way, the fluid is required to alter course only twice, rather than the usual four tums required by current bypass tools. Further, the amount of course alteration required by the slanted exit ports is substantially less than ninety degrees:, resulting in greatly lessened flow rate losses compared to current bypass tools. The lower velocities for a given flow rate have the additional advantage of lessening erosion of the bypass tool.
A retrievable memory gauge is also provided to read pressure and temperature data during gravel packing. This gauge is designed to collect data without being disturbed by the fluid flow passing through the ports above the gauge.
A High-Rate Multizone Gravel Pack System is provided that allows significantly higher gravel packing flow rates for a tool of a given size than were previously available. This system includes a fluid bypass which greatly enhances flow rate and decreases damage to the bypass due to erosion compared to current tools. The system can be employed in a multi-stage arrangement which allows the gavel-packing of multiple production zones with a single trip into the well bore.
It is a goal of this invention to provide a bypass tool that incurs lower fluid pressure losses compared to present bypass tools.
It is a further goal of this invention to provide a bypass tool that allows higher gravel packing flow rates at a formation than are allowed by present bypass tools.
It is another goal of this invention to provide a bypass tool that is less subject to erosion than present bypass tools.
It is another goal of this invention to provide a multi-zone gravel packing system that allows gravel packing at high flow rates in multiple production zones with a single trip of the apparatus into the well bore.
It is another goal of this invention to provide a retrievable memory gauge capable of sensing and recording pressure and temperature during gravel packing without being disturbed by the fluid flow through the bypass tool.